yup there are schools and labs around, those are costly and i feel that the only way to learn and remember is to do a small project with it.
if the cost of "school" is out of your range, then that kills that idea ... but I didn't mean that the school would (necessarily) TEACH you the subjects that you want to learn ... I meant that if the lab equipment is locally available, then the cost of a semester might give you access to the hardware and software - and might be cheaper in the long run than buying your own stuff ... just tell the instructor to stay out of your way - and let you play with the toys ...
am planning to write my own drivers for the PLC and not using standard scada / hmi softwares like ifix , wonderware etc.
there are many threads on the forum covering ideas like yours ... let me ask you something (it's ok if you choose not to answer) ... how old are you? ... and are you planning to ever make money in this automation field? ... if you're still quite young, then maybe you have time to have fun - and learn a LOT - from what you're talking about doing ... if you're old enough to be "getting on with your life" - then maybe you need to carefully consider whether this project will ultimately be worth the time (and money?) that you're about to devote to it ...
something to consider: if you're thinking about making this a career, try to find someone to talk to about your course of action ... hopefully that would be someone like a prospective employer who could tell you honestly what you need to know - and what type of skills they would find attractive if considering hiring you in the future ... people here on the forum could certainly give you the same type of advice - as long as you tell them enough about what you want to do ...
finally ... if you're young enough - then DO whatEVER you want to do ... you'll always regret it if you don't ...
PS EDIT: heck, even if you're getting on in years - go ahead and DO whatEVER you want to do ... as long as you don't have to neglect any important responsibilities (family, etc.) to do it ...
again, I wish you the best of good fortune ...